﻿//https://leetcode.cn/problems/number-of-islands/?envType=problem-list-v2&envId=depth-first-search

class Solution {
    int dx[4] = { 0,0,1,-1 };
    int dy[4] = { 1,-1,0,0 };
    bool vist[301][301];
    int ret = 0, n = 0, m = 0;
public:
    int numIslands(vector<vector<char>>& grid)
    {
        m = grid.size();
        n = grid[0].size();
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                if (!vist[i][j] && grid[i][j] == '1')
                {
                    dfs(grid, i, j);
                    ret++;
                }
            }
        }
        return ret;
    }


    void dfs(vector<vector<char>>& grid, int i, int j)
    {
        vist[i][j] = true;
        for (int k = 0; k < 4; k++)
        {
            int a = i + dx[k], b = j + dy[k];
            if (a >= 0 && a < m && b >= 0 && b < n && !vist[a][b] && grid[a][b] == '1')
            {
                dfs(grid, a, b);
            }
        }
    }
};